Benign White Cell Disorders: Reactive
Lymphadenopathy

REACTIVE LYMPHOID HYPERPLASIA is the benign and
reversible enlargement of lymphoid tissue secondary to
antigen stimulus. The lymph node response to stimuli varies.
Follicles can increase in size and number; sinuses can
enlarge and fill with histiocytes, or the architecture can
be diffusely effaced by sheets of lymphocytes, a few
immunoblasts and macrophages. In some cases there is a
mixture of follicular, sinus and diffuse patterns.

Each of these morphologically recognizable
patterns is associated with certain antigenic stimuli, thus
the morphologic type of lymphadenopathy may offer clues as
to the etiology of the lymphadenopathy.

FOLLICULAR HYPERPLASIA is characterized by enlargement of
lymph nodes by hyperplasia of follicular (germinal) centers.
At right, note the variablilty in the size of the follicles
and the presence of mantle zones in the reactive node.

In FOLLICULAR HYPERPLASIA, the hyperplastic germinal
center contains a normal mixture of varibly sized
lymphocytes, plasma cells, and macrophages, as well as a few
dendritic reticular cells. No one lymphocyte type
predominates as in lymphoma.

In SINUS HYPERPLASIA the sinuses become distended and
filled with histiocyte/macrophages and some plasma cells.

In DIFFUSE HYPERPLASIA the lymph node architecture is
diffusely effaced by sheets of small lymphocytes, and a few
scattered immunoblasts and macrophages.

MIXED HYPERPLASIA is a combination of follicular, sinus
and diffuse patterns of hyperplasia.

Morphologic patterns of reactive lymphoid
hyperplasia and their associated disorders.

Morphologic patterns of reactive lymphoid hyperplasia
and their associated disorders.

DIFFUSE

post-vaccinial lymphadenitis

anticonvulsant therapy

viral lymphadenitis

dermatopathic lymphadenopathy

MIXED

infectious mononucleosis

toxoplasmosis

cat scratch disease

tuberculosis

In addition to the aforementioned hyperplasias other
diseases, i.e., histiocytosis X and metastatic carcinoma can
involve lymph nodes causing a reactive hyperplasia or mimic
a hyperplasia (Histiocytosis X in the sinuses of a lymph
node) and thus need to be carefully ruled out on microscopic
exam.

Department of Pathology

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